This application is related to and claims priority from Japanese Patent Applications No. Hei. 11-279972 filed on Sep. 30 1999, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a double heat exchanger having several core portions such as a condenser core for a vehicle refrigerant cycle and a radiator core for a vehicle engine.
2. Description of Related Art
In a conventional double heat exchanger described in JP-A-10-103893, plural protrusion portions are provided in a radiator header tank to partially contact a condenser header tank. However, during brazing, melted brazing material flows from the protrusion portion of the radiator header tank to a contact portion between the protrusion portion and the condenser header tank to be collected at the contact portion by a capillary phenomenon. Therefore, after the brazing, the contact area between the protrusion portion and the condenser header tank increases. Accordingly, the heat of the cooling water in the radiator is transmitted to refrigerant in the condenser, and the heat-radiating capacity of the condenser is decreased.
In view of the foregoing problems, it is an object of the present invention to provide a double heat exchanger having first and second cores which prevents a decrease of the heat-radiating capacity due to the heat transmission between the first and second cores.
According to the present invention, in a double heat exchanger with a first core and a second core, a protrusion is provided on a first header tank communicating with plural first tubes of the first core. The protrusion has a contact part contacting a contact surface of a second header tank communicating with plural second tubes of the second core. In the double heat exchanger, a coating-removing restriction material for restricting the removal of an oxidation coating formed on the surface of a brazing material is added to either the contact part of the protrusion or the con tact surface of the second header tank. Therefore, it can prevent the melted, brazing material from flowing from the protrusion to the contact surface of the second header tank due to a capillary phenomenon during brazing. Accordingly, a heat-transmitting area between the first header tank and the second header tank is not increased, and a decrease of heat-radiating capacity of the double heat exchanger due to heat-transmission between both first and second header tanks can be restricted.
Preferably, the coating-removing restriction material is magnesium. Therefore, it is possible for either the contact part of the protrusion or the contact surface of the second header tank to be made of an aluminum alloy including magnesium. Alternatively, on either the contact part of the protrusion or the contact surface of the second header tank, a paste-like magnesium material can be added as the coating-removing restriction material. Accordingly, the moving of the melted brazing; material due to the capillary phenomenon can be restricted.
More preferably, the protrusion is provided by a bracket attached to the first header tank, and the bracket is formed separately from the first and second header tanks. Therefore, are protrusion can be easily formed.
Further, the protrusion is disposed to form a clearance around the protrusion between the first header tank and the second header tank, and the clearance is set to a range of 0.5 mm-1.5 mm. Therefore, it can further restrict melted brazing material from collecting between the protrusion and the contact part contacting the second header tank by the capillary phenomenon during brazing. Accordingly, a decrease of heat-radiating capacity due to the heat transmission between the first and second cores can be further restricted.